A control system typically includes a controller and a plant (e.g., a motor driving a load). The plant is connected to the controller through a feedback loop. In operation, the plant is controlled by output of the controller. Output of the plant is fed back to the controller via the feedback loop and is subtracted from a reference input to form an error signal. This error signal is processed by the controller to generate a modified control input to the plant.
A controller typically includes filters and control algorithms. Control algorithms amplify error signals and add feed-forward terms to create command signals. These control algorithms are tuned to maintain optimized command response, disturbance rejection, stability, and noise susceptibility in the presence of changes in characteristic properties such as plant inertia, resonance due to compliance, backlash, friction etc.
Control algorithms, such as PID (Proportional-Integral-Derivative) control algorithms, are widely used. A PID type control algorithm is so named because its control output is derived from a weighted sum of a term proportional to the input, a term proportional to the integral of the input, and a term proportional to the derivative of the input. Such control algorithms include a proportional amplification unit with a proportional gain parameter, KP, an integration unit with an integration gain parameter, KI, and a derivative unit with a derivative gain parameter, KD.
Tuning control algorithms includes setting or adjusting associated gains to achieve desired performance. Since stability of a motion controller may vary due to interaction with load condition, for example, gains of the control algorithms should be tuned (adjusted) regularly to operate effectively for the specified application. Poorly tuned control algorithms either act aggressively or sluggishly, or with insufficient margins of stability. When uncertainty in disturbance or process dynamic characteristics is large, tuning of control algorithms is often difficult. As a result, the tuning process usually requires manual tuning by an experienced technician. Manual tuning, however, can be tedious and non-optimal.